[tex]4x + 5y = - 2 \\ 5y = - 2 - 4x \\ y = \frac{ - 2}{5} - \frac{4x}{5} \\ [/tex]
so the slope of the line m is a=-4/5
let a' be the slope of the line perpendicular to m ,
a.a'=-1 ( Perpendicular lines )
-4/5 x a'=-1
a'=
[tex] \frac{ - 1}{ \frac{ - 4}{5} } = \frac{5}{4} [/tex]
